Hi, Looking for info on steam holes and location on Casting #3774692 small block heads. Info out there states they were made from 58-64. Were the holes present in all these heads from 1958-64. Cannot find difference in photos of earlier heads. Corvette by the numbers states that they were first started with the 61 head! What purpose did they serve? Was there an overheating problem or circulation problem with the motors? Thanks Don.
I thought they have to do with the SB 400 due to the siameses bores. I wasn't aware they were done so early though.
steam hole are on sb 400. they had overheating problems because of the siameses cyd. you can use an head gasket for a template if you need to drill a head to work on a 400 block.
I am aware of the 400 's having steam holes. If the Corvette book is correct they are stating that the 61 head was drilled for steam holes and previous heads were not! Was there a heating issues? My vette runs up there on a hot day and have gone thru everything twice. Thought possibly the steam holes or lack of may be causing a problem. Books shows the head the same from 58-64.The photos of the chamber side all look the same. No info out there on this.
I think Bob is right, don't go drilling anything, totally different subject for 400's only. Chevy did make some casting changes in the early years and I don't recall all of them but there is nothing you can do to fix your heads. I would check elsewhere for the causes of the overheating.
Friend who worked at GM Desert Proving Grounds had a set of drawings done by GM for NASCAR that showed where to drill and where to plug small blocks (both heads and block). This mod would lower operating temp by 20 degrees and even cooling out in engine to prevent hot spots. He did this mod to his Nomad and I did it to my 327 that was in my '33 at the time. It did lower temps (even in traffic in AZ in the summer) I used to have a set of the drawings but haven't seen them lately (I've moved twice since using them) I'm sure others have the same drawings.........
Hi, I agree I am not drilling holes. The Corvette book states "Four steam pockets have been added to the underside of the head" The photos they show and all previous photos of combustion side of heads are the same! I do not see anything extra. I contacted an expert this evening on these motors and hopefully can get an answer. These heads are for a 1961 283 engine. I decided to post it here because of the vast knowledge that this site has! Thanks , Don.
As far as I know the 400 didn't come out until 1970, so those must be something other than steam holes. Where do they line up in the block? Maybe they're for oil drain back?
I think it is the Spark plug cooling holes he is talking about. Very early heads had no extra cooling, but as HP increased the spark plugs life dropped because of heat. A cooling passage was added, I have seen early heads that were cast with the trough cast in but the connector holes undrilled, later they were all drilled to allow the coolant to pass through the trough cast into the head below the plug. Why anyone calls a passage in a cooling jacket of a motor a steam passage is beyond me ? They are really cooling passages as there is no air to make steam. In a 400 small block and many other motors cast with siamese cylinders a vent hole is used to release trapped air between the cylinders. This is to prevent steam from forming in a trapped pocket.
O.K. I can believe that! It makes sense and most of the photos do not show the trough well enough to allow you to see a hole in the ends.I agree steam holes or pockets is a wrong term. I only have known that term used with the 400 engine. I will contact some one from the book to see if they can clarify what was written. Purchasing another block for the vette and he was not aware of the so called steam holes or pockets either. Thanks to one and all. I will post when I get more info and investigate further. Thanks Don.
O.K. Got some info on this! Turns out that the area in question is called a "trench" and not steam pocket or holes as written in places. Yes the area is below the spark plug in the combustion side of the head as some of you know.Earlier photos of the head have this area missing and about 1958 there is a trench milled out. GM was having trouble in cooling things so that was a step in the right direction. The horse power was on the increase and the cooling was becoming an issue.The refrence to the 1961 head having a change was that they drilled holes in the end of the trench if i understand it correctly to further cool the area! The books refrence does not go into any detail so that is the confusion. I got the info from a guy that has alot of experience with the early heads. Now I can look for the correct heads I need even though the head may have the correct casting number on it. Thanks again for all the help out there. You guys and gals are a brain trust and I do appreciate it. Thanks Don.
Hey Don your guys nomenclature is right. I now realize you throw food into a trough and throw water into a trench. Ha Ha
I hear you. Been a mechanic all my life and paid attention to what I was doing I thought? I will attest that when I run into these problems now, I have to sit back and think about how to resolve the problem! I have always learned from others and will continue to learn! As I said before there is a ton of info and intelligence on this site. I marvel at the subjects and the people that have knowledge and help solve questions. New chapter on "EARLY HEADS 101 ". Thanks Don
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